Expandable bead molding



Dec. 2l, 1965 R. G. BRIDGES ET AL 3,225,125

EXPANDABLE BEAD MOLDING Original Filed Oct. lO. 1960 8 Sheets-Sheet lDec. 21, 1965 R, G, BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING Original Filed Oct. l0. 1960 8 Sheets-Sheet 2 ww@Q Dec. 21, 1965 R. G. BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING Original Filed Oct. 10. 1960 8 Sheets-Sheet 5/f/'Zzza Dec. 21, 1965 R. G. BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING Original Filed Oct. 10. 1960 8 Sheets-Sheet 4Dec. 21, 1965 R. G. BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING 8 Sheets-Sheet 5 Original Filed Oct. l0. 1960.www

Dec. 21, 1965 R. G. BR|DGEs ET AL 3,225,126

EXPANDABLE BEAD MOLDING original Filed oct. 1o. 1960 s sheets-sheet emy" Si -f R. G. BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING l Dec. 2l, 1965 8 Sheets-Sheet '7 Original FiledOct. 10, 1960 Dec. 21, 1965 R. G. BRIDGES ETAL 3,225,126

EXPANDABLE BEAD MOLDING 8 Sheets-Sheet 8 Original Filed OCT.. l0. 1960United States Patent O 3,Z25,l26 EXPANDABLE BEAD MLDENG Roy G. Bridges,Rivera, Robert N. Aleson, San Fernando,

Douglas B. Hutchings, North Hollywood, Ralph E.

Whited, Altadena, and Miron L. Dyrness, North Hollyu Wood, Calif.,assignors to 'liernpo Plastic Company, inc.,

Los Angeles, Calif., a corporation of @ailier-nia Original applicationct. iti, i960, Ser. No. 61,566.

Divided and this application May 6, i963, Ser. No.

3 Claims. (Cl. 26d-51) This application is a division of co-pendingapplication Serial No. 61,566, iiled October 10, 1960, for ExpandableBead Molding, and now abandoned.

This invention relates to a method for molding expandable plastic beadsand the objects formed by such molding.

Articles made by the expansion of plastic beads have been commerciallyavailable for some time. One of the most widely distributed of sucharticles has been cups molded from polystyrene beads. A device formolding such cups is shown in U.S. Patent No. 2,951,260. Cups and otherarticles made by the expansion of piastic beads have heretofore commonlysuffered from an excessive brittleness, often being crushed duringhandling or use. Furthermore, the automatic molding of -a variety ofobjects has not been possible heretofore, such automatic orsemi-automatic molding having been limited to thinwalled objects, suchas cups.

The plastic beads most often utilized in this type of molding arepolystyrene beads, which are commerci-ally available from a number ofmanufacturers. In order to obtain a molded product of uniform 'lowdensity, the beads are commonly su-bjected to a preliminary processingknown as pre-expansion, in which the unconned expansion of the beads isinduced. A variety of methods and types of apparatus may be utilized toaccomplish preexpansion, For example, the unexpanded beads may becontinuously fed into an upright drum. At the base thereof, steam isinjected into the drum to heat the beads, thus causing expansion. Thedrum preferably contains revolving agitators to prevent bead fusionduring preeXpans-ion. As the beads expand their bulk density decreases.The pre-expanded beads therefore rise to the top of the drum, and may beremoved therefrom by a simple overflow outlet. Pre-expanded beads foruse in cup molding are expanded to have a density preferably of from oneto ten pounds per cubic foot, although densities as high as fifty poundsper cubic foot are practicable.

According to the present invention, an improved method is utilized toproduce a molded object of improved characteristics, particularly, withrespect to brittleness. The invention is especially appropriate forproducing an improved polystyrene cup from preexpanded polystyrenebeads. The improved cup so produced has greater lieX- ibility than cupsheretofore available, while retaining or improving the other desirablecharacteristics of such cups. These improved characteristics areproduced in the molding of other objects as well and it is to beunderstood that the invention is generally applicable to the automaticmolding of thin or thick walled objects yfrom expandable plastic beadsand includes the objects so molded. rlhe invention is described hereinspecifically with respect to the molding of the cups from polystyrenebeads. The molding of cups and the use of polystyrene beads is not,however, to be considered as restricting the practice of the inventionto such material or to the molding of such objects.

A molded plastic object according to the preferred embodiment of thepresent invention is formed from beads which have been pre-expanded, ifdesired, according to well-known methods. The pre-expanded beads are Cil3,225,126 Patented Dec. 21, 1965 ice injected into the cavity of aheated mold. Concurrent with the expansion of lthe pre-expanded beadsdue to the mold temperature, in the preferred embodiment, steam isinjected into the mold cavity so as to be in intimate contact with thebeads. In the preferred embodiment, the cavity is also vented duringmolding. 'The expansion of the pre-expanded beads Within the mold,resulting from the cooperative effects of the mold temperature,injection of steam into the mold cavity, and venting of the cav-ity,forms a plastic object having an improved characteristic of rigiditywith resp-ect to such objects as were known heretofore.

The improved method of making objects according to the presentinvention, in its preferred embodiment, contemplates injecting beads,which have been pre-expanded, if desired, into the cavity of a heatedmold, expanding the beads Within the mold cavity by the concurrentapplication of `heat from the mold and injection of steam into thecavity, together with the venting of the cavity during molding, coolingthe cavity, and subsequently removing the object from the cavity.

The apparatus for the practice of the invention consists, in general, ofa mold assembly, having as a first component, a shell portion, and, lasa second component, a core portion. Either of these components includesa sub-component portion, which is selectively movable relative to itsmajor component to eject the molded object from the assembly. Whenmolding cups or the like, it is preferred that the core portion includethe core proper and the sub-component, designate-d as the stripper ring,which is detachable from the core. Alternate structures lalso suitablefor molding cups of other objects in practicing the invention, which donot use a stripper ring as such, but do include a subcomponentassociated either with the shell portion or the core portion andselectively relatively movable with respect .thereto are contemplated bythe invention. In the apparatus, means are provided to inject steam,hereinafter referred to as cooking steam, into the mold cavity tocontact .the beads during molding. The cavity is preferably ventedduring at least a substantial portion of the molding. Means are includedto provide steam at two temperatures, hereinafter referred to 4as highpressure steam and low pressure steam, and cooling water, to each of thethree mold components. Exhaust means are provided to remove the high andlow pressure steam, cooling Water and cooking steam from the moldassembly. Means are provided to open and close the mold assembly. Aprogrammer, connected. to the aforementioned means, is utilized toinitiate automatic cyclical mol-ding. While the present form of theappanatus is described with respect to the use of high and low pressuresteam, cooling water and cooking steam, it is to be understood that theinvention is not limited to the utilization of these fluids solely. Anyfluid of appropriate characteristics and temperature inlay be utilizedin place of any of the preceding fluids. Furthermore, with the exceptionof the cooking steam, none of these fluids contacts the beads, and sincetheir function is solely heating or cooling, other means of heating orcooling can be substituted therefor.

Means are provided to fill the closed mold cavity at a preselected timewith beads contained in a bin. In the preferred embodiment, the beadshave been pre-expanded, and are injected into the mold cavity by meansof cornpressed air. The necessity for metering the amount of beads to befed into the mold cavity is eliminated by the utilization of compressedair, in conjunction with bead feeding apparatus and mold apparatus andmethod o1' the present invention. By utilizing the present invention,bead feeding and molding are not restricted by the requirement that thequantity of beads to be injected into 9 the mold be metered or measured.The requirements that gravity of feed for beads be used and that themold be disposed so as to have that portion of the mold cavity intowhich the beads are fed in an elevated disposition with respect to theremainder of the cavity are eliminated.

The invention may be more readily understood by referring to theaccompanying drawings in which:

FIGURE 1 is a block schematic of apparatus for the molding of cups frompolystyrene beads according to the present invention;

FIGURE 2A is a side elevation of the mold apparatus of FIG. 1 in itsopened position;

FIGURE 2B is a side elevation of a portion of the apparatus of FIG. 2A;

FGURE 3A is a side elevation of the mold apparatus of FIG. l in itsclosed position;

FIGURE 3B is a side elevation of a portion of the apparatus of FIG. 3A;

FIGURE 4 is a view, partially in section, of the mold in its closedposition;

FIGURE 5 is an end view, partially in section, of the mold shellcomponent;

FIGURE 6 is an end view of the mold core component;

FIGURE 7 is a side elevation of an end plate which closes the corecomponent;

FIGURE S is an end view of the stripper ring cornponent;

FIGURE 9 is an end view, partially in section, of the slide plate whichcloses the shell; and,

FIGURE 10 is a timing chart illustrating the timing sequence for controlof the apparatus by the programmer.

Referring now to FIG. 1, a mold assembly, indicated generally at 10, isshown in its opened position. The mold assembly lltl includes a shellportion lll, a stripper ring 12, and a core 13. The shell il. andstripper ring 12 are attached to first and second mounting plates 15 and16, respectively. The core 13 is connected to a third mounting plate 17by means of four standoff lugs 118, only two of which are shown inFIG. 1. Four aligning bars 19, only two of which are shown in FIG. 1,extend between the rst mounting plate 15 and a fourth mounting plate 20.rIhe second and third mounting plates 16 and 17 are mounted on thealigning bars 119, so as to be movable therealong between the rstmounting plate l5 and the fourth mounting plate Ztl. An air cylin* der21 is attached to the fourth mounting plate 20 and has a piston rod 22extending therefrom and through the fourth mounting plate 2t?. Thepiston rod 22 is attached to the third mounting plate 17. The first aircylinder 21 has a lirst compressed air control valve 24 connected to twocontrol lines 25 and 26, which extend into the cylinder 21 on eitherside of a piston (not shown) positioned therewithin. The piston rod 22is connected to this piston. When actuated by the control valve 2d,compressed air is selectively applied to one or the other of the controllines 25, 26 and enters the cylinder ZI, causing the piston to move. Thepiston movement moves the piston rod 22 and thus the third mountingplate 17 toward or away from the Iirst mounting plate I5, as isappropriate.

The first and fourth mounting plates 15 and 2@ are shown in FIG. 1 asbeing of greater length than the second and third mounting plates I6 andI7. Such additional length is utilized to indicate that, in thepreferred embodiment of the apparatus shown in FIG. l, the first andfourth mounting plates 15 and 2@ are secured to a frame assembly (notshown) for the apparatus, or to the structure in which the apparatus ishoused, so as to be fixed in position. The second and third mountingplates 16, 17, as will be subsequently explained, move between theposition shown in FIG. l, and a position adjacent the rst mounting plateI5. These two positions, the open and closed positions of the moldassembly 10, are more clearly shown in FIGS. 2 and 3. However, it is tobe understood that the apparatus of the invention can be modified sothat the second mounting plate 16 is xed in position and the rst andthird mounting plates I5, 17 are movable, thus selectively moving thecore 13 and the shell llt away from the stripper ring 112 to open themold assembly. Also, the apparatus can be modified so as to have thethird mounting plate 17 fixed in position, and the first and secondmounting plates I5, f6 then being movable with respect thereto so as toprovide for the moving of the shell Il and stripper ring ik away fromthe core 1 3 to open the mold assembly 19.

A cooking steam inlet valve 3i) is connected to a source of cookingsteam 3l; a cooling water inlet valve 32, to a source of cooling water33, a low pressure steam inlet valve 34., to a source of low pressuresteam 35; a high pressure steam inlet valve 36, to a source of highpressure steam 37; a vacuum control valve 38, to a source of vacuum 39;and a bead blow back valve du, to a source of compressed air 4l. rIhesource of compressed air 41 is also applied to a second air cylindercontrol valve i2 which is associated with a second air cylinder 43. rPhecompressed air from the second air cylinder control valve 42 is suppliedto the second air cylinder 43 through either of two air cylinder inletlines 44 or 45. The second air cylinder d?, has a piston (not shown)which is connected to a piston rod 46, shown as extending from thecylinder 43.

A cooking steam exhaust valve 5@ -is connected to a cooking steam outlet5l; and a high and low pressure steam and cooling water exhaust valve52, to a high and low pressure steam and cooling water outlet 53. Eachof the control valves 30, 32, 34, 35, 3S, di?, 5@ and 52 are ofconventional construction and can be, for example, solenoid controlvalves. These valves are connected to a programmer 55. The programmercontrols the opening and closing of each of the valves in the apparatus,with the exception of a swing check valve 56, which is connected to theoutlet of the vacuum control valve 3S and closes when the vacuum controlvalve 33 opens.

The cooking steam inlet valve 3) is connected to the core 13 through acooking steam inlet line 69, which connects through an end plate (notshown, see FIG. 3A) to the interior of the core 13. Cooking steam 31passing into the interior of the core I3, escapes therefrom through aplurality of apertures 62 of fluid conduits (not shown, see FIG. 4)which extend through the wall of the core 13. The cooling water, lowpressure steam, and high pressure steam inlet valves 32, 34, 36,respectively, are connected to a manifold 65. The manifold 65 isconnected to the core 13 by a first manifold outlet line 66, to thestripper ring i2 by a second manifold outlet line 67, and to the shell1I by a third manifold outlet line 68. The vacuum control valve 3S isconnected to the stripper ring 12 by a vacuum inlet line 69. The swingcheck valve 56 is connected to the vacuum inlet line 69 by a vacuumconnecting line 70. Thus, the swing check valve 56 is open to vent thestripper ring when the vacuum control valve 33 is closed. The secondcompressed air control valve 4@ is connected to the shell 11 by acompressed air connecting line 71 to provide for bead blow back, as willsubsequently be explained.

A cooking steam exhaust line 75 is connected between the core I3 and thecooking steam exhaust valve 50. A rst high and low pressure steam andcooling water exhaust line 76 is connected between an outlet connector77 of the core assembly 13 and the high and low pressure steam andcooling water exhaust valve 52. The valve 5?, also has connected theretoa second exhaust line 78, which is connected to the stripper ring I2,and a third exhaust line 79, which is connected to a slide plateassembly Si). A high and low pressure steam and cooling water transferline Si is connected between the shell Il and the slide plate assemblySu, so as to apply the high and low pressure steam and cooling waterwhich has passed through the shell 11 to the slide plate assembly 80.The lines 81 and 79 are connected to the slide plate assembly 80 so thatthe high and low pressure steam and cooling water from the transfer line01 pass through the slide plate assembly 80 and into the exhaust line79. A dotted line 82 indicates this passage through the slide plateassembly 80.

The slide plate assembly 80 is movable in response to actuation of thesecond air cylinder 43. A bead blow back passage, indicated by thedotted line 84, extends through the shell 11 and communicates with abead passage, indicated by the dotted line 85, in the slide plateassembly 80. A bead blow back outlet pipe 86 is connected to apositioning plate 87, which is fixed in position with respect to theshell 11. Therefore, as the slide plate assembly 80 moves in response tothe actuation of the second air cylinder 43, relative motion occursbetween the positioning plate S7 and the slide plate assembly 80.

Also connected to the positioning plate S7 is a preexpanded bead inletpipe 88. The pre-expanded bead inlet pipe 8S extends into a bin 89,shown partially in section, having pre-expanded beads 90 therewithin.Although preferable when using polystyrene beads, the use ofpre-expanded beads is not essential, so long as the beads used areexpandable. A compressed air line 92, connected at one end to a sourceof compressed air 93, extends through the bin 90 into the pre-expandedbead inlet pipe 83.

FlGURE 2A is a side elevation of the mold assembly 10 in its openedposition. A molded cup 100 is shown in position in the stripper ring 12.A cup stripper arm 101 is illustrated as in contact with the cup. Inactual operation, the stripper arm 101 strikes the cup 100 prior to themold assembly 10 reaching its opened position so as to knock the cup 100from the stripper ring 12. The stripper arm 101 is connected to astripper linkage 102 consisting of a first arm 103, to which thestripper arm 101 is attached, and a second arm 104. The first arm 103and the second arm 104 are connected together by a pin joint 105. Thefirst arm 103 is pivotally connected to an arm support 106 and thesecond arm 104 pivotally connected to an arm support 107. The first andsecond arm supports 106 and 107 are attached, respectively, to thesecond and third mounting plates 16 and 17, by means of bolts 108.

A latching arm 110 has a pivotal connection 111 with the third mountingplate 17. The latching arm 110 terminates at one end thereof in a nose112. A latch pin 113 extends outwardly from the second mounting plate16. The latching arm 110 has a latching groove 114 adjacent the nose 112and a camming surface 115 at the opposite end thereof. A cam 116 isattached to the fourth mounting plate by a pair of bolts 117. Aduplicate latching assembly (not shown) is provided on the opposite sideof the mold assembly 10. A stop plate 118 is attached to the thirdmounting plate 17 by means of a pair of bolts 119. The stop plate 118functions to limit the rotary movement of the latching arm 110.

The second mounting plate 16 has a first pair of stop pads 120 and 121(stop pad 121 being partially broken away to show the core 13) attachedthereto. The first mounting plate 15 -has a second pair `of stop pads124 and 125 (stop pad 125 being broken away) attached thereto. Thestripper ring 12 is attached to the second mounting plate 16 by means offour bolts 126 (only two of which are shown in FIG. 2A), which extend,one each, through apertures (not shown, see FIG. 8) in four attachinglugs 127 radiating outwardly from the stripper ring periphery.

The shell 11 is attached to the first mounting plate 15 by means of apair of parallel mounting bars 129 (only one of which is shown in FIG.2A), to which an attaching fiange 130 of the shell 11 is connected bymeans of bolts 131. The mounting bars 129 are connected to the firstmounting plate 15 by bolt assemblies (not shown).

The second and third mounting plates 16 and 17 have mounting sleeves 135attached thereto which enclose the aligning bars 19.

In FIG. 2B, the mounting of plates 15, 16, 17, 20 are shown with thealigning bars 19, -air cylinder 21, piston rod 22, and stop pads 121,125. The remaining portions of the assembly have been omitted forpurposes of clarity. Attached to the second mounting plate 16 are a pairof stop rods 130 (only one is shown in FIG. 2B), each of whichterminates in a stop face 131. A stop sleeve 132 is mounted on each ofthe stop rods 130 so as lto be disposed between the stop face 131 andthe third mounting plate 17. The rods 130 extend through passages 134 inthe third mounting plate 17 When the mold assembly is in the openposition shown in FIG. 2B, the second mounting plate 16 is held a fixeddistance from the fourth mounting plate 20 by the stop rod 130. Thethird mounting plate 17 rides against the stop sleeve 132 due to theretracting action of the piston rod 22. The second and third mountingplates 16, 17 are thus also held fixed distances from the fourthmounting plate 20.

FIGURE 3A is an elevation of the mold assembly 10 and related componentsin their closed position. The mold assembly 10 is closed as a result ofthe actuation of the first air cylinder 21, so as to extend the pistonrod 22 in the direction of the first mounting plate 15. As the thirdmounting plate 17 moves from the fourth mounting plate 20 under theinfluence of the piston rod 22, the latch camming surface disengages thecam 116 and the latching arm 110 assumes a horizontal position, due tocounterweighting means (not shown) on the latching arm 110 adjacent thelatching groove 114. A spring may be utilized as an alternative tocounterweighting. The nose 112 then rides over the latch pin 113, andthe latching groove 114 engages the latch pin 113. The third mountingplate 17 contacts the stop pads 120, 121, which are attached to thesecond mounting plate 16. Further movement of the third mounting plate17 under the influence of the piston rod 22 therefore moves the secondmounting plate 16 as well as the third mounting plate 17. The second andthird mounting plates 16 and 17 continue to move in the direction of thefirst mounting plate 15, under the influence of the piston rod 22, untilsuch time as the second mounting plate 16 contacts the stop pads 124 and125. The movement of the second and third mounting plates 15 and 16 isthereby terminated, and the mold assembly 10 is in its closed position.

FIGURE 3B illustrates the disposition of the portions of the moldassembly shown in FIG. 2B when the mold assembly is closed. The stop pad121 has been partially broken away, as has the third mounting plate 17,in order to more clearly illustrate the structure. It will be noted thatthe stop rod face 131 is no longer in contact with the fourth mountingplate 20, the second mounting plate 16 now riding against the stop pad125. The third mounting plate 17 now rides against the stop pad 121instead of against the stop sleeve 132.

The mold assembly 10 is shown in its closed position in FIG. 4. Theshell 11 includes an outer hollow frustoconical Wall 140 and an innerhollow frustoconical wall 141, illustrated in the preferred embodimentas having spiral ribs 142 around the outer surface of 'the inner wall141. The outer wall 140 has an outer wall attaching flange portion A,and the inner wall 141 has an inner wall attaching iiange portion 130B.rThe outer and inner walls 140, 141 are connected together by boltspassing through the flange portions 130A and 130B. Alternatively, otherconventional means, such as welding, may be utilized to connect theouter and inner walls and 141 together. The inner surface of the innerwall 141 is smooth and, when made of aluminum has a finish depositedthereon which, in order to insure long mold life, is preferably of ahardness in excess of 70 Rockwell C. An example of such a finish is thewell known San- 7 ford finish. This finish has a hardness ofapproximately 72 Rockwell C.

Thus spiral ribs 142 form a spiral lfuid passage between the inner andouter walls 140, 141 of the shell 11. A lluid inlet 145, having athreaded portion 146, is formed in the attaching flange so as tocommunicate with this fluid passage. A lluid outlet 148, having athreaded portion 149, is formed in an end flange 150 of the shell 11,and communicates with the lluid inlet through the lluid passage formedby the spiral ribs 142. The attaching llange 130 has an annular recess151 on the inner portion 130B thereof.

It should be noted that the end flange has the bead blow back passage 84extending therethrough. A bead blow back hose, which is the compressedair connecting line 71, is connected to the bead blow back passage 84 bya hollow bolt 152, around the head of which line 71 is clamped. Ofcourse, other types of connections can be used. The bead blow backoutlet pipe 86 is xed to the positioning plate 87 by means of a cap,bolt and washer combination 153. The pre-expanded bead inlet pipe 88 issimilarly attached to the positioning plate 87 by a cap, washer and boltcombination 154. The bead inlet pipe 88 is shown as being substantiallysmaller than the adjacent open end of the shell 13. In manyapplications, it has been found advantageous to make either the beadinlet pipe 87 or the inlet passage 88 or both comparatively larger thanthe relative sizes shown.

The slide plate assembly 80 is positioned adjacent the end llange 150 ofthe shell 11 iso as to be slightly spaced therefrom to provide cavityventing. A clearance of three thousandths of an inch has been found tobe appropriate in order to vent the cavity to permit the cooking steamto freely Contact all of the beads in the mold cavity, While notresulting in beads filling this clearance space during molding. Thisventing also enables trapped gases in the cavity to escape. The slideplate assembly 80 has a recessed body portion at the lower end thereof,into which a plurality of arcuate ribs 156 extend. A cover plate 157seals the recessed body portion 155 and is held in position by threebolt and washer combinations 158 (only one of which is shown in FIG. 4).An O-ring 159, positioned in a peripheral groove of the cover plate 157,seals the recessed portion 155. A iluid inlet indicated by the dottedlines 160 has an opening 161 in the recessed body portion 155. Thetransfer line 81 is connected to the inlet 161. A lluid outlet (notshown, see FIG. 9) opens into the opposite side of the recessed bodyportion 155. The third exhaust line 79 is connected to this fluid inlet.

The stripper ring 12 has a vacuum connecting passage including athreaded portion 171 at the external end thereof. The vacuum connectingpassage 170 has a rst branch 172 and a second branch 173, the functionsof which will be subsequently explained. The rst branch 172 terminatesat a pair of lips 174 which engage the annular recess 151 of theattaching llange 130B. The inner lip can be made to protrude less farthan the outer lip, in order to assure leakage therearound so as toapply vacuum to the mold cavity, as will be explained subsequently. Thestripper ring 12 has a hollow recessed portion 175 therein, which ismore clearly shown in FIG. 8. The hollow recessed portion 175 is sealedby means of a sealing ring 176, which is held in position by a snap ring177. The seal is completed by a pair of O-rings 178, which arepositioned in grooves in the inner and outer surfaces of the sealingring 176. The snap ring 177 is held in position by a pair of outershoulders 179A and inner shoulders 179B.

The core 13 includes outer and inner walls 180 and 181, similarly tothose described with respect to the shell. The inner wall 181 has ribs182 extending radially outwardly therefrom. The ribs 182 are illustratedas parallel rather than spiral. However, it is to be understood that therib 182 may be made to be spiral, if desired, or that the spiral ribs142 of the shell 11 may be parallel. The ribs 182 have slots 190therein, which allow the passage of fluid between adjacent spacesintermediate between the ribs 182 while providing lluid bailling. Theribs 182 have holes drilled therethrough which coincide with holes inthe core outer wall 180. Rivets are inserted in these holes. The rivethead at the outer wall 180 is smoothed so as to be llush with the coresurface. Fluid conduits 183, formed through the rivet, terminate in thecooking steam apertures 62. A finish, preferably of a hardness greaterthan 70 Rockwell C, is applied to the core surface when the core outerwall 180 is made of aluminum. This finish may also be the Sanford finishpreviously referred to. The inner wall 181 and outer wall 180 can beattached together by any conventional means to assist the rivets inholding the walls 180, 181 in a xed disposition with respect to eachother.

A cup mold cavity 200 is formed between the shell inner wall 141, coreouter wall 180, with the lip of the cup being completed by a shoulder201 on the shell inner wall and a shoulder 202 on the stripper ring 12.The outer botwall 180 has a solid end 203, which forms the inner bottomof the cup 100. The inner core wall 181 has an end 204, which has athreaded aperture 205 extending therethrough. A fluid outlet pipe 206 isthreaded in this threaded aperture 205. The inner core end 204 and theouter core end 203 are connected to each other by hollow rivets 208which extend through supporting lugs 209 and have cooking steamapertures 62A to permit the passage of cooking steam into the endportion of the cup mold cavity 200.

A lluid inlet 215, having a threaded portion 216, extends through theouter core wall 180 adjacent the stripper ring 12 and opens into thespace between the core inner and outer walls 180 and 181. The slots 190in the ribs 182 provide a baflled lluid passage between the lluid inlet215 and the iluid outlet pipe 206. This ballling insures good fluidcirculation to provide adequate heat transfer characteristics.

An end plate 220 is attached to the core 13 so as to close a cookingsteam space 221 formed within the core inner wall 181. The end plate 220has a fluid outlet pipe aperture 222 through which fluid outlet pipe 206passes. A seal between the end plate 220 and fluid outlet pipe 206 isformed by an O-ring 223 which is positioned in a groove formed about thelluid outlet pipe aperture 222. A. cooking steam inlet passage 225,having a threaded portion 226, extends through the end plate 220 andopens into the cooking steam space 221 at an inlet aperture 227. Acooking steam outlet passage 228, having a threaded portion 229, extendsfrom an outlet aperture 230 through the end plate 220 from the cookingsteam space 221. The inlet and outlet apertures 227 and 230 are formedin a core insert portion 231 of the end plate 220.

FIGURE 5 is a view, partially in section, of the open end of the shell11. The lluid inlet 145, a portion of the end flange 150 and the beadblow back passage 84 are shown by dotted lines. In the portion partiallybroken away and shown in section, the disposition of the inner portion130B and outer portion 130A of the attaching flange 130 are shown, asare the outer wall 140 and inner wall 141 of the shell 11 and one of thespiral ribs 142. Around the inner periphery of the attaching portioninner llange 130B, the annular recess 151 and cavity lip-formingshoulder 201 are shown.

FIGURE 6 is a view lof the open end of the core 13. One of the ribs 182and the slot 190 therein are shown by the dotted lines. The relativedisposition of the three supporting lugs 209 is shown by the location ofthe hollowed rivets 208 which extend therethrough and were describedwith respect to FIG. 4. The core 13 has a core end flange 250 having anend plate mounting slot 251 extending therethrough. The slot 251 isadapted to receive the end plate 220. Four end flange attaching aper- 9tures 252 extend through the end flange slot 251, and are utilized toattach the end plate 220 to the end flange 250. The end ange 250 alsohas four stand-off lug attaching apertures 255, which are utilized toattach the stand-off lugs 18 to the core 13.

FIGURE 7 is an end view of the end plate 221i. The core insert portion231, and cooking steam inlet passage 225, inlet aperture 227, outletpassage 228 and outlet aperture 230 are shown by dotted lines. The uidoutlet pipe aperture 222 extends through the end plate 220. Four coreattaching apertures 257 extend through the end plate 220 and aredisposed to be in alignment with the four end flange attaching apertures252 (FIG. 6) in the core 13 when the end plate 22@ is inserted in theend plate mounting slot 251 so that the uid outlet pipe 2116 extendsthrough the aperture 222 in the end plate 221). The end plate 22d andcore 13 are attached together by nut and bolt combinations (not shown).Of course, any conventional attaching method may be utilized in thealternative.

An end view of the stripper ring 12 is shown in FIG. 8. The vacuumconnecting passage 171i, first branch opening 172, and second branchopening 173 are shown by dotted lines. For purposes of clarity, dottedlines indicating the pair of lips 174 are omitted. A rst connectingpassage 266, to which the second manifold outlet line 67 (FIG. l) isconnected and a second connecting passage 261, to which is connected thesecond exhaust line 78, are shown by dotted lines, and open into thehollow recessed portion 175. Each of the attaching lugs 127 has a hole263 extending therethrough, through which a bolt 126 (see FIG. 2)extends to attach the stripper ring 12 to the second mounting plate 16.

FIGURE 9 is an end View of the slide plate assembly 80, positioningplate 87, and shell end iiange 150. The positioning plate 87 and coverplate 157 have been partially broken away to show the arcuate ribs 156in the recessed body portion 155 of the slide plate assembly Si). Inaddition, a iiuid outlet passage 290 is shown, which was previouslyreferred to with respect to FIG. 4, and to which the third exhaust line79 is connected. The uid outlet passage 299 has an opening 291 whichopens into the recessed body portion 155. The slide plate assembly 80 isconnected to the end flange 15@ by means of a pair of slide plateholders 295. The slide plate assembly 30 has a pair of ribs 296 whichengage slots (not shown) in the slide plate holders 2%. Spacer plates294 are positioned between the slide plate 80 and end ange 150 toprovide cavity venting during molding. T he slide plate holders 295 andspacer plates 294 are attached to the end flange 151) by means of bolts298. The slide plate assembly S is thus free to move vertically but isrestrained from horizontal movement. The positioning plate 87 isseparated from the slide plate 80 by spacer plates 297 and attached tothe slide plate holders 295 by means of bolts 299 which extend throughapertures (not shown) in attaching arms 3111) of the positioning plate87. The bolt and washer assemblies 158 and positioning plate S7 providevertical stops for the vertical movement of the slide plate assemblySti. However, in normal operation, the vertical movement of the slideplate assembly Si) is such as to not normally require this stop functionto be utilized. Dotted lines indicate the positioning of the beadpassage 85 when the slide plate assembly 80 is in the lowered positionutilized to fill the mold cavity with pre-expanded beads 9i) through thepreexpanded bead inlet pipe 88.

FIGURE 10 illustrates the timing sequence followed in the preferredmethod of practicing the invention. The mold assembly opening is takenas the cycle initiation time, although, as a practical matter, the cycleis continuous and not susceptible to having any single` point designatedas the time of cycle initiation. The numbers across the top of the chartmay be considered as indieating time intervals in seconds. It is to beunderstood that the time intervals given may be varied while stillobtaining satisfactory molding. In addition, ambient conditions, such ashumidity and temperature, may make advisable some deviation from thetime intervals shown. However, such deviations do not depart from thescope of the invention, and the timing Sequence of FIG. l0 is given sothat the invention may be more easily understood and practiced. As hasalready been stated, the use of the terms high pressure steam, lowpressure steam, cooking steam, and cooling water are not tot beconsidered as limiting the practice of the invention to these particulariluids. Any fluid having appropriate characteristics may be substitutedfor any of the aforementioned uids.

Coincident with the opening of the mold assembly 1t), high pressuresteam is applied to the manifold 65 by the opening of the high pressuresteam valve 36. The high pressure steam is utilized to pre-heat the mold11) to substantially the temperature at which molding takes place.Appropriate conditions for the high pressure steam are saturated steamat a pressure of 80 p.s.i.g. At the time the mold assembly 1t) isopened, vacuum is being applied to the stripper ring 12 due to theopening of the vacuum inlet valve 38 and the closing of the vacuum checkvalve 56. The high and low pressure steam and cooling water exhaustvalve 52 is also open, as is the cooking steam exhaust valve 50.

About one-half second after the mold assembly 10 commences to open,which is substantially the time interval required for the secondmounting plate 16 to become unlatched from the third mounting plate 17,the vacuum valve is closed. Cooking steam is applied to the core 13 bythe opening of the cooking steam inlet valve 3@ at a time one andone-half seconds after the mold assembly 10 opens. The cooking steam 30may be saturated steam at a pressure of 28 p.s.i.g. The mold assembly 10remains open for approximately two and one-half seconds, during whichtime the cup stripper arm 1111 frees the molded cup 1191i from thestripper ring 12. The cup falls away from the mold assembly 141 due tothe eifect of gravity. The mold assembly 1li then closes two andone-half seconds after` opening.

At the time the mold assembly 10 closes, the cooking steam exhaust valve50 is open to vent the cooking steam space 221. The high and lowpressure steam and cooling water exhaust valve 52 is also open, insuringa rapid ow of high pressure steam through the shell 11 and core 13battle systems. In the middle of the fourth time interval, i.e., threeand one-half seconds after the mold assembly 1t) opens, the highpressure steam valve closes, terminating the pre-heating of the core 13and shell 11. At the end of the fourth time interval, the cooking steaminlet valve closes, and the vacuum inlet valve opens. The application ofthe vacuum to the mold cavity through leakage around the lip-formingshoulder 202 of the stripper ring 12 reduces the pressure existingwithin the mold cavity. The cavity walls have been heated to atemperature preferably of about 265 Fahrenheit by the high pressuresteam. The combination of this temperature and reduce-d pressuretlash-vaporizes any moisture which may have condensed in the cavity 200and exhausts the vapor through the leakage around the stripper ringlip-forming shoulder 202. In order to assure a rapid reduction inpressure, it is preferred to provide the previously mentioned clearancebetween the inner of the pair of lips 174 and the lip-forming shoulder201 of the shell, as has been pointed out with respect to FIG. 4.

Midway through the fifth time interval, the cooking steam exhaust valve50 and the high and low pressure steam and cooling water exhaust valve52 close, and the low pressure steam inlet valve 34 opens. lLow pressuresteam, which may be saturated steam at a pressure of 25 p.s.i.g., isthen applied to the stripper r-ing 12, core 13 and shell 11.

At the middle of the sixth time interval, the bead blovil back valve d@opens, applying compressed air to the bead blow back passage 84 to clearthe bead passage 85 for the injection of pre-expanded beads 9@ into themold cavity 200. I ust prior to the end of the sixth time interval, thesecond air cylinder control valve S2 is actuated to cause the slideplate 80 to move its lower position, so as to align the bead passage S5with the pre-expanded bead inlet pipe 88. The bead blow back valve 40then closes.

Pre-expanded beads 9@ are injected into the mold cavity 2li@ by theforce of the compressed air applied to the preexpanded bead inlet pipe88 by the compressed air line 92. The application of vacuum to thestripper ring l2 insures that the beads fill the mold cavity 26)especially that portion forming the cup lip. Shortly after the start ofthe eighth time interval, the slide plate assembly is returned to itsupper position, terminating the injection of beads 90 into the cavity200. The vacuum inlet valve 33 closes. The bead blow back valve 40 isthen opened briefly to clear the bead passage 55 of beads which remaintherein after the mold cavity 290 was filled. If the bead passage 85 isnot cleared, the beads remaining therein may expand and clog thepassage, so that the subsequent bead injection into the mold will not bepossible.

The cooking steam inlet valve 3@ is opened at the middle of the eighthtime interval to apply cooking steam to the pre-expanded beads in themold cavity 2MB. The cooking steam exhaust valve Sil is opened briey atthis time to vent the air in the cooking steam space 221, so that thecooking steam space 221i is rapidly filled with cooking steam. Thecooking steam inlet valve Sti closes at the end of the eleventh timeinterval, i.e., eleven seconds after the opening of the mold assemblyll) in the example given.

Midway during the thirteenth time interval, the low pressure steam inletvalve 34 closes, and the mold cooling cycle commences. The cooking steamexhaust valve 5t) and the high and low pressure steam and cooling waterexhaust valve 52 open. The cooling water inlet valve 32 opens, applyingcooling water to the manifold 65, from which it passes to the core L3,shell lll]` and stripper ring 12. The bead blow back valve 4@ is alsoopened briefly to remove any cooking steam condensate which may haveaccumulated.

At the end of the fourteenth time interval, the cooking steam exhaustvalve 50 closes, the temperature of the mold assembly lil having beenreduced to a temperature such that any cooking steam has either beenexhausted or condensed.

The cooling water inlet valve 32 closes at the middle of the nineteenthtime interval, and the cooking steam exhaust valve S@ simultaneouslyopens. The cooking steam exhaust valve 50 is opened in order tofacilitate removal of the cup from the core 13 after the mold assemblyll@ opens. Just prior to the opening of the mold assembly llt), thevacuum inlet valve 38 opens, and vacuum is applied to the lips of thecup MM5, which has been formed within the cavity 200. When the moldassembly lli commences to open, this vacuum insures that the cup will bedrawn out of the shell lll by the movement of the stripper ring 12. Atthe time when the stripper ring 12 movement stops, the core 13 continuesto move. In order to prevent the existence of a vacuum between the cupl@ and the core 13, the opened cooking steam outlet l permits thepassage of air through the cooking steam apertures 62 upon withdrawal ofthe core 13 from the cup ltl. Otherwise, a vacuum might result whichwould cause the cup 100 to deform. However, the necessity forapplication of compressed air to core apertures required by the priorart is eliminated by the invention. Thus, a cycle of the moldingapparatus has been completed and the apparatus now commences a secondsuch cycle to form another cup.

The mold assembly l@ is constructed from conventional materials. Forexample, aluminum or steel may be utilized. The cavity walls Ml, 180 maybe of one-eighth inch thickness when made of aluminum, or ofone-twentieth of an inch thickness when made of stainless steel. An

aperture diameter of eighteen-thousandths of an inch for the sides andtwenty-thousandths of an inch for the bottom has been found to besatisfactory for the cooking steam apertures 62 and 62A. Of course,while the apertures 62 and 62A are shown as formed in the core wall 189,they can equally well be formed in the shell wall 141, or in both. Itis, however more convenient structurally to form the apertures in thecore i3 and utilize the core center as the cooking steam space 221. Theapertures may range in diameter from ten to thirty-thousandths of aninch for thinwalled objects, and range up to one-sixteenth of an inchfor thickwalled objects. The cavity 290 may have a width of threethirty-seconds of an inch when molding cups or other thinwalied objects,thus forming a cup having walls of this thickness. Heretofore, it hasnot been possible to form cups by the application of steam directly topre-expanded polystyrene beads in a mold cavity of only this thickness.The conventional practice has required only indirect bead heating duringmolding of cups when cavity thicknesses of less than one-quarter inchhave been utilized, and cooking steam and venting have not been utilizedheretofore successfully to produce objects automatically, regardless ofwall thickness.

When utilizing steam of the pressures given in the foregoing descriptionof operation, cooling water at a temperature of about 83 Fahrenheit, avacuum of 22 inches, and compressed air at a pressure of p.s.i.g. areappropriate values. The operation of the apparatus may be readilymonitored by measuring the temperature of fluid existing in the transferline 8l. A conventional thermocouple may be used for such a measurement.Optimum operation utilizing the above conditions has been found toresult when the operating temperatures within the transfer line 81 fallwithin ten degrees of the following mean temperatures:

Temperature at the time of closure of high pressure steam inlet valve-265 Fahrenheit;

Temperature during molding-initially 260 Fahrenheit, rising to 264Fahrenheit at the time of closure of low pressure steam inlet valve;

Temperature during coolingfalling rapidly from a temperature of 264Fahrenheit when the cooling water inlet valve opens to a temperature ofFahrenheit when the cooling water valve closes.

The optimum conditions have been found to vary from day to day, due tochanges in ambient conditions and to the aging of the pre-expandedbeads. The aging of the pre-expanded beads is an importantconsideration, since it has been found that temperature adjustmentswithin a ten degree range are necessary to compensate for changes in thephysical characteristics of the beads which occur as a result of storageboth before and after pre-expansion. ln addition, the bulk density ofthe pre-expanded beads has an important effect upon the optimumtemperature conditions for operation. The above temperatures areespecially appropriate for utilization with pre-expanded beads of a bulkdensity of between one and ten pounds per cubic foot, and are usuallysatisfactory up to fifty pounds per cubic foot. This range of beaddensity has been found to be the optimum range of density for makingcups. Cups made from lighter densities do not have the requiredstrength, while cups made from heavier densities tend to lose some oftheir insulating characteristics, due to the extreme density of theirconstruction.

The programmer utilized to control the operation of the apparatus is ofconventional construction. A wide variety of such programmers areavailable. Perhaps the simplest such programmer is a motor-drivenelectrically conductive belt. An electrical potential is applied to thebelt. Each of the control circuits terminates in one of an array ofcontact arms which ride against the belt, so as to provide continuouselectrical circuits. Insulating strips are applied to the belt tointerrupt the continuity of the electrical control circuits asappropriate to provide the actuation and deactuation of the variousvalves of the apparatus. For example, referring to FIG. l0, the beltwould have insulating strips corresponding to the blank portions andelectrical conductivity between the belt and the contact arms wouldoccur in the shaded portions. Of course, a variety of more elaboratesystems for control can be devised, and it is to be understood the useof such systems constitutes practice of the present invention, which, inits broad aspects, is not limited to any particular control apparatus,as distinguished from the novel method and apparatus for practice ofapplicants invention, and the novel objects made thereby.

The invention has been described in its preferred embodiment, whichincludes the application of cooking steam to the mold cavity concurrentwith the venting of the mold cavity, which takes place throughout themolding period of the cycle. However, the invention may also bepracticed by the utilization of these tivo elements in cooperationduring only a portion of the molding portion of the cycle. Thus, thecooking steam may be applied throughout the molding portion, While thecavity is vented during only a portion of this time interval. Toaccomplish this, vent passages may be provided in the slide plate tovent the cavity when the slide plate is in an intermediate position, forexample. Other systems, such as a vent valve assembly, can be used.Furthermore, the cavity can be vented throughout the molding portion ofthe cycle, and cooking steam applied to the mold cavity throughout thistime interval. Such a modification is readily accomplished by adjustmentof the programmer. in addition, While `it is to be understood that it ispreferred to utilize cooking steam and cavity venting during molding incooperation, as has been described heretofore, a significant improvementover the prior art is provided by the utilization of either theapplication of cooking steam to the mold cavity during molding or theventing of the cavity during molding, when articles are to beautomatically molded from expandable beads.

As used herein, the term venting of the cavity refers to providing apassage for the escape of fluid from the cavity during molding, asdistinguished from during the filling of the cavity with beads, and isnot limited to such a passage directly communicating with theatmosphere, and the term application of cooking steam to the mold refersto providing the presence of cooking steam or other appropriate fluidWithin the mold cavity.

The invention claimed is:

1. The method of forming a cup with pre-expanded polystyrene beads in acup mold cavity, the method consisting of the steps of preheating themold cavity, injecting the pre-expanded beads into the pre-heatedcavity, concurrently and coextensively applying heat to the mold from afirst source and applying steam at substantially the same temperature asis the average temperature to which the mold cavity is preheated to themold cavity from a second source, so as to cause the beads to expand andfill the mold cavity, and removing the formed cup from the mold cavity.

2. The method of claim 1 and including the step of ventin g the moldcavity during molding.

3. The method of making a cup with pre-expanded polystyrene beads in aheated cup mold having a male part and a female part which fit togetherto form a mold cavity, the method consisting of the steps ofsubstantially filling the cavity of the mold with pre-expanded beads,and expanding the pre-expanded beads Within the mold cavity by theconcurrent and independent application of steam to the cavity and ofheat to the mold so that the beads expand and fill the cavity Whileventing the cavity at a location separate from the points of steam ofapplication and removing the cup from the cavity.

4. The method of making a cup from pre-expanded polystyrene beads in aheated cup mold defining a mold cavity consisting of the steps ofsubstantially filling the cavity of a heated cup mold with pre-expandedbeads,

expanding the pre-expanded beads Within the mold cavity by theconcurrent application of heat to the mold-through a first conduit meansand to the mold cavity through a second conduit means, the applicationof heat to the mold being independent of the application of. heat to themold cavity so that the beads expand and ll the cavity While venting thecavity through a third conduit means and removing the cup from thecavity.

5. A method for automatically molding objects from expandable beadsconsisting of cyclically repeating the steps of closing a mold havingfirst, second, and third parts which fit together to form a mold cavity,heating the mold cavity, injecting expandable beads into the cavity,concurrently and coextensively applying heat to the mold from a firstsource and to the mold cavity from a second source While venting thecavity to form a molded object within the cavity from the beads, coolingthe cavity, moving the first part of the mold relative to the second andthird parts to clear the molded object from the first part, moving thesecond part relative to the third part to clear the molded object fromthe second part and thereafter removing the molded object from the thirdpart.

6. A method for automatically molding; objects from expandable beadsconsisting of cyclically repeating the steps of closing a mold havingfirst, second and third parts which lit together to form a mold cavity,preheating the mold cavity, injecting expandable beads into the cavity,concurrently and coextensively applying steam to the mold from a firstsource and cooking steam to the mold cavity from a second source whileventing the cavity at a location separate from the sources of steamapplication to form a molded object Within the cavity from the beads,cooling the cavity, moving the first part of the mold relative to thesecond and third parts to clear the molded object from the first part,moving the second part relative to the third part to clear the moldedobject from the second part and thereafter removing the molded objectfrom the third part.

7. The method of making a cup with pre-expanded polystyrene beads in acup mold cavity, the method consisting of the steps of injecting thepre-expanded beads into the cavity of a cup mold which has beenpreheated from a temperature substantially greater than ambient tosubstantially 265 Fahrenheit, concurrently and coextensively maintainingthe mold at a temperature of substantially 265 Fahrenheit by means ofheat from a first source and applying steam from a second source at atemperature at substantially 265 Fahrenheit to the mold cavity through aplurality of apertures which extend through one of the cavity walls andhave a diameter of between ten and thirty-one thousandths of an inch, s0as to cause the beads to expand and fill the cavity, cooling the mold,and removing the formed cup from the mold cavity.

3. The method of claim 7 and including the step of venting the moldcavity during molding.

References Cited by the Examiner UNITED STATES PATENTS 2,951,260 9/1960Harrison et al. 264-53 XR 2,954,589 10/1960 Brown 264-51 XR 2,977,6394/1961 Barkhuff et al 264-45 3,069,725 12/1962 Root 264-51 3,086,2484/1963 Culp 264-53 3,099,045 7/1963 Honkanen 264-51 XR 3,125,780 3/1964Harrison et al 18-5 OTHER REFERENCES Koppers: Technical manual Dyliteexpandable polystyrene, Mold Techniques and Mold Designs, ch. 3e,Bulletin C-9-273, Nov. 15, 1959, all pages.

Koppers: Technical manual Dylite expandable polystyrene, Mold Filling,ch. 3d, Bulletin C-9-273, Nov. l5, 1959, all pages.

ALEXANDER H. BRODMERKEL, Primary Examiner.

1. THE METHOD OF FORMING A CUP WITH PRE-EXPANDED POLYSTYRENE BEADS IN ACUP MOLD CAVITY, THE METHOD CONSISTING OF THE STEPS OF PREHEATING THEMOLD CAVITY, INJECTING THE PRE-EXPANDED BEADS INTO THE PRE-HEATEDCAVITY, CONCURRENTLY AND COEXTENSIVELY APPLYING HEAT TO THE MOLD FROM AFIRST SOURCE AND APPLYING STEAM AT SUBSTANTIALLY THE SAME TEMPERATURE ASISS THE AVERAGE TEMPERATURE TO WHICH THE MOLD CAVITY IS PREHEATED TO THEMOLD CAVITY FROM A SECOND SOURCE, SO AS TO CAUSE THE BEADS TO EXPAND ANDFILL THE MOLD CAVITY, AND REMOVING THE FORMED CUP FROM THE MOLD CAVITY.